Elastomeric bicomponent fibers comprising block copolymers having high flow

ABSTRACT

Bicomponent fibers comprising a thermoplastic polymer and an elastomeric compound are made which can be continuously extruded from the melt at high production rates. The elastomeric compound has high flow and consists essentially of a selectively hydrogenated block copolymer and a tackifier resin, an alpha-olefin copolymer, an alpha-olefin terpolymer, a wax or mixtures thereof. In one embodiment the block copolymer has at least one polystyrene block of molecular weight from 5,000 to 7,000 and at least one polydiene block of molecular weight from 20,000 to 70,000 and having a vinyl content of greater than 60 mol %. In a second embodiment the block copolymer has a vinyl content of less than 60 mol %. The bicomponent fibers are useful for the manufacture of articles such as woven fabrics, spun bond non-woven fabrics or filters, staple fibers, yarns and bonded, carded webs.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. provisional patent application Ser. No. 60/549,570, filed Mar. 3, 2004, entitled Block Copolymers having High Flow and High Elasticity and is a continuation-in-part of U.S. patent application Ser. No. 11/069,286, filed Mar. 1, 2005, entitled Elastomeric Bicomponent Fibers Comprising Block Copolymers having High Flow.

FIELD OF THE INVENTION

The invention relates to bicomponent fibers comprising a thermoplastic polymer and an elastomeric compound. In particular the elastomeric compound has high flow and comprises a block copolymer of mono alkenyl arene and conjugated diene blocks and any one of a tackifying resin, an alpha olefin copolymer, an alpha olefin terpolymer, a wax or mixtures thereof. The invention further relates to articles made from bicomponent fibers.

BACKGROUND

Fibers made from elastic materials find use in a variety of applications ranging from woven fabrics to spunbond elastic mats to disposable, personal hygiene items. It would be of particular interest to use styrenic block copolymers for such applications. However, the typical phase-separated nature of block copolymer melts leads to high melt elasticity and high melt viscosity. In order to process styrenic block copolymers through small orifices, such as found in fiber spinnerets, expensive and specialized melt pump equipment would be required. Further, the high melt elasticities lead to fracture of the fiber as it exits the die, preventing the formation of continuous elastomeric fibers. As a result, styrenic block copolymers have been found to be exceedingly difficult to process into continuous elastic fibers at high processing rates.

A further problem with styrenic block copolymers is their inherent stickiness in the melt. Because of this character, melt spun fibers of styrenic block copolymers tend to stick together, or self-adhere, during processing. This effect is not desired and can be, in fact, tremendously problematic when separate, continuous fibers are the goal. In addition to the result of an unacceptable fiber product, the self-adhesion of the fibers leads to equipment fouling and expensive shut-downs. Efforts to apply styrenic block copolymers in elastic fiber production have to date been met with significant challenges.

Himes taught the use of triblock/diblock copolymer blends as one approach to make elastomeric fibers in U.S. Pat. No. 4,892,903. These types of compositions have been found to have high viscosities and melt elasticities which have limited them to formation of discontinous and continuous fibers such as used in melt-blown, non-woven applications.

Bicomponent fibers comprising acid functionalized styrenic block copolymers have been taught by Greak in European Patent Application 0 461 726. Conventional, selectively hydrogenated styrenic block copolymers which were acid functional were used to form side-by-side bicomponent fibers with polyamides. While the acid functionalization provided increased adhesion between the two components, it is well known in the art that acid functionalization leads to even higher melt viscosities and melt elasticities than in unfunctionalized block copolymers. Further, the side-by-side morphologies taught by Greak would not prevent the inherently sticky fibers from self-adhering during processing.

Bonded non-woven webs made using bicomponent fibers comprising, among other polymers, conventional styrenic block copolymers and having a variety of morphologies has been taught by Austin in U.S. Pat. No. 6,225,243. In particular, the sheath-core morphologies, with the core being comprised of styrenic block copolymers, provided fibers of suitably low stickiness to form non-woven webs.

However, high viscosity and melt elasticity of conventional styrenic block copolymers continues to prevent high speed spinning of continuous elastomeric fibers. The present invention addresses these longstanding needs by providing a high melt flow block copolymer which is able to be formed into continuous elastomeric bicomponent fibers.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a bicomponent fiber comprising a thermoplastic polymer and an elastomeric compound wherein the elastomeric compound consists essentially of a selectively hydrogenated block copolymer having an S block and an E or E₁ block and having the general formula: S-E-S, (S-E₁)_(n), (S-E₁)_(n)S, (S-E₁)_(n)X or mixtures thereof, wherein:

-   -   a. prior to hydrogenation the S block is a polystyrene block;     -   b. prior to hydrogenation the E block is a polydiene block,         selected from the group consisting of polybutadiene,         polyisoprene and mixtures thereof, having a molecular weight         from 40,000 to 70,000;     -   c. prior to hydrogenation the E₁ block is a polydiene block,         selected from the group consisting of polybutadiene,         polyisoprene, and mixtures thereof, having a molecular weight         from 20,000 to 35,000;     -   d. n has a value of 2 to 6 and X is the residue of a coupling         agent;     -   e. the styrene content of the block copolymer is from 13 to 25         weight percent;     -   f. the vinyl content of the polydiene block prior to         hydrogenation is from 70 to 85 mol percent;     -   g. the block copolymer includes less than 15 weight percent of         units having the general formula:         S-E or S-E₁     -   wherein S, E and E₁ are as already defined;     -   h. subsequent to hydrogenation about 0 to 10% of the styrene         double bonds have been hydrogenated and at least 80% of the         conjugated diene double bonds have been hydrogenated;     -   i. the molecular weight of each of the S blocks is from 5,000 to         7,000;         and a tackifying resin.

In another aspect, the present invention is a bicomponent fiber comprising a thermoplastic polymer and an elastomeric compound wherein the elastomeric compound consists essentially of a selectively hydrogenated block copolymer having an S block and an E or El block and having the general formula: S-E-S, (S-B₁)_(n), (S-B₁)_(n)S, (S-E₁)_(n)X or mixtures thereof, wherein:

-   -   a. prior to hydrogenation the S block is a polystyrene block;     -   b. prior to hydrogenation the E block is a polydiene block,         selected from the group consisting of polybutadiene,         polyisoprene and mixtures thereof, having a molecular weight         from 40,000 to 70,000;     -   c. prior to hydrogenation the E₁ block is a polydiene block,         selected from the group consisting of polybutadiene,         polyisoprene, and mixtures thereof, having a molecular weight         from 20,000 to 35,000;     -   d. n has a value of 2 to 6 and X is the residue of a coupling         agent;     -   e. the styrene content of the block copolymer is from 13 to 25         weight percent;     -   f. the vinyl content of the polydiene block prior to         hydrogenation is from 35 to 50 mol percent;     -   g. the block copolymer includes less than 15 weight percent of         units having the general formula:         S-E or S-E₁     -   wherein S, E and E₁ are as already defined;     -   h. subsequent to hydrogenation about 0 to 10% of the styrene         double bonds have been hydrogenated and at least 80% of the         conjugated diene double bonds have been hydrogenated;     -   i. the molecular weight of each of the S blocks is from 5,000 to         7,000         and any one of a tackifying resin, an alpha-olefin copolymer, an         alpha-olefin terpolymer, a wax or mixtures thereof.

In another aspect, the present invention is a bicomponent fiber comprising a thermoplastic polymer and an elastomeric compound wherein the elastomeric compound consists essentially of a selectively hydrogenated block copolymer having an S block and an E or E₁ block and having the general formula: S-E-S, (S-E₁)_(n), (S-E₁)_(n)S, (S-E₁)_(n)X or mixtures thereof, wherein:

-   -   a. prior to hydrogenation the S block is a polystyrene block;     -   b. prior to hydrogenation the E block is a polydiene block,         selected from the group consisting of polybutadiene,         polyisoprene and mixtures thereof, having a molecular weight         from 40,000 to 70,000;     -   c. prior to hydrogenation the E₁ block is a polydiene block,         selected from the group consisting of polybutadiene,         polyisoprene, and mixtures thereof, having a molecular weight         from 20,000 to 35,000;     -   d. n has a value of 2 to 6 and X is the residue of a coupling         agent;     -   e. the styrene content of the block copolymer is from 13 to 25         weight percent;     -   f. the vinyl content of the polydiene block prior to         hydrogenation is from 70 to 85 mol percent;     -   g. the block copolymer includes less than 15 weight percent of         units having the general formula:         S-E or S-E₁     -   wherein S, E and E₁ are as already defined;     -   h. subsequent to hydrogenation about 0 to 10% of the styrene         double bonds have been hydrogenated and at least 80% of the         conjugated diene double bonds have been hydrogenated;     -   i. the molecular weight of each of the S blocks is from 5,000 to         7,000         and any one of an alpha-olefin copolymer, an alpha-olefin         terpolymer, a wax or mixtures thereof.

In another aspect the invention is an article such as an elastomeric mono filament, a woven fabric, a spun bond non-woven fabric, a melt blown non-woven fabric or filter, a staple fiber, a yarn or a bonded, carded web comprising the bicomponent fiber described herein.

Importantly, the invention comprises an elastomeric compound having high melt flow which allows processing of bicomponent fibers on commercial-type equipment at high rates. The high melt flow of the elastomeric compound can be achieved with selectively hydrogenated block copolymers having high vinyl contents, sufficiently low molecular weights, presence of high flow components such as tackifying resins, alpha-olefin copolymers, alpha-olefin terpolymers or waxes, or by some combination of these features.

FIGURES

FIG. 1 shows a cross-section of a bundle of bicomponent fibers of the present invention having a sheath-core morphology. The sheath is comprised of a thermoplastic polymer and is apparent as an annular region surrounding each core which is comprised of an elastomeric compound.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The bicomponent fibers of the present invention comprise a thermoplastic polymer and an elastomeric compound comprising a selectively hydrogenated block copolymer, a tackifying resin, an alpha olefin copolymer, an alpha olefin terpolymer, a wax or mixtures thereof. The bicomponent fiber is made by a coextrusion process in which the thermoplastic polymer and the elastomeric compound are metered to a die or spinneret separately. Such a coextruded bicomponent fiber can have a variety of morphologies including, but not limited to, sheath-core, side-by-side, islands in the sea, bilobal, trilobal, and pie-section.

In the sheath-core embodiment of the present invention it is important that the sheath form the majority of the outside surface of the fiber. In particular, the sheath-core morphology wherein the sheath forms a covering about the core is one preferred embodiment. In this preferred morphology, the core may be centered in the fiber cross-section or may be off-center. The sheath may cover the core in a complete fashion over the circumference of the fiber or may be only partially covering over the circumference of the fiber. In the case where the covering is partial about the circumference, the core makes up the majority of the volume of the fiber. The volume ratio of the sheath to the core in the present invention is from 1/99 to 50/50. The preferred range of sheath to core volume ratio is 5/95 to 40/60 and the most preferred range is 10/90 to 30/70. The sheath consists primarily of a thermoplastic polymer and the core consists of an elastomeric compound. As used herein “consists primarily” means greater than 80% on a volume basis.

In the islands-in-the-sea embodiment of the present invention it is important that the sea form a continuous matrix in which the islands exist. The islands-in-the-sea morphology is another preferred embodiment. The islands are referred to as such because of their appearance in cross-sectional views of the coextruded bicomponent fiber. The islands are actually microfibrous elements embedded in the continuous sea matrix. In this preferred embodiment the sea consists primarily of a thermoplastic polymer and the islands consist primarily of an elastomeric compound. The volume ratio of the sea to the islands in the present invention is from 1/99 to 50/50. The preferred range of sea to island volume ratio is from 5/95 to 40/60 and the most preferred range is from 10/90 to 30/70. It is well known in the art that free-standing microfibers can be produced from coextruded bicomponent fibers having islands-in-the-sea morphologies. Such microfibers are obtained by removing the sea matrix by a process such as selective dissolution. In this way, the free-standing microfibers remain. The bicomponent fibers of the present invention are suitable for producing elastomeric microfibers comprising the elastomeric compound.

In one embodiment the elastomeric compound comprises a selectively hydrogenated block copolymer having an S block and an E or E₁ block and having the general formula: S-E-S, (S-E₁)_(n), (S-E₁)_(n)S, (S-E₁)_(n)X or mixtures thereof, wherein: (a) prior to hydrogenation, the S block is a polystyrene block; (b) prior to hydrogenation, the E block or E₁ block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof. The block copolymer can be linear or radial having three to six arms. General formulae for the linear configurations include: S-E-S and/or (S-E₁)_(n) and/or (S-E₁)_(n)S wherein the E block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof, having a molecular weight of from 40,000 to 70,000 ; the E₁ block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof, having a molecular weight of from 20,000 to 35,000; and n has a value from 2 to 6, preferably from 2 to 4, an more preferably an average of approximately 3. By example, the general formula for the radial configurations having three and four arms include:

wherein the E₁ block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof, having a molecular weight of from 20,000 to 35,000 ; and X is a coupling agent residue.

As used herein, the term “molecular weights” refers to the true molecular weight in g/mol of the polymer or block of the copolymer. The molecular weights referred to in this specification and claims can be measured with gel permeation chromatography (GPC) using polystyrene calibration standards, such as is done according to ASTM 3536. GPC is a well-known method wherein polymers are separated according to molecular size, the largest molecule eluting first. The chromatograph is calibrated using commercially available polystyrene molecular weight standards. The molecular weight of polymers measured using GPC so calibrated are styrene equivalent molecular weights. The styrene equivalent molecular weights may be converted to true molecular weights when the styrene content of the polymer and the vinyl content of the diene segments are known. The detector used is preferably a combination ultraviolet and refractive index detector. The molecular weights expressed herein are measured at the peak of the GPC trace, converted to true molecular weights, and are commonly referred to as “peak molecular weights”.

The block copolymers of the present invention are prepared by anionic polymerization of styrene and a diene selected from the group consisting of butadiene, isoprene and mixtures thereof. The polymerization is accomplished by contacting the styrene and diene monomers with an organoalkali metal compound in a suitable solvent at a temperature within the range from about −150° C. to about 300° C., preferably at a temperature within the range from about 0° C. to about 100° C. Particularly effective anionic polymerization initiators are organolithium compounds having the general formula RLi_(n) where R is an aliphatic, cycloaliphatic, aromatic, or alkyl-substituted aromatic hydrocarbon radical having from 1 to 20 carbon atoms; and n has a value of 1 to 4. Preferred initiators include n-butyl lithium and sec-butyl lithium. Methods for anionic polymerization are well known and can be found in such references as U.S. Pat. Nos. 4,039,593 and U.S. Reissue Pat. No. Re 27,145.

The block copolymers of the present invention can be linear, linear coupled, or a radial block copolymer having a mixture of 2 to 6 “arms”. Linear block copolymers can be made by polymerizing styrene to form a first S block, adding butadiene to form an E block, and then adding additional styrene to form a second S block. A linear coupled block copolymer is made by forming the first S block and E block and then contacting the diblock with a difunctional coupling agent. A radial block copolymer is prepared by using a coupling agent that is at least trifunctional.

Difunctional coupling agents useful for preparing linear block copolymers include, for example, methyl benzoate as disclosed in U.S. Pat. No. 3,766,301. Other coupling agents having two, three or four functional groups useful for forming radial block copolymers include, for example, silicon tetrachloride, methyl-trichlorosilane, dimethyl-dichlorosilane and alkoxy silanes as disclosed in U.S. Pat. Nos. 3, 244,664, 3,692,874, 4,076,915, 5,075,377, 5,272,214 and 5,681,895; polyepoxides, polyisocyanates, polyimines, polyaldehydes, polyketones, polyanhydrides, polyesters, polyhalides as disclosed in U.S. Pat. No. 3,281,383; diesters as disclosed in U.S. Pat. No. 3,594,452; methoxy silanes as disclosed in U.S. Pat. No. 3,880,954; divinyl benzene as disclosed in U.S. Pat. No. 3,985,830; 1,3,5-benzenetricarboxylic acid trichloride as disclosed in U.S. Pat. No. 4,104,332; glycidoxytrimethoxy silanes as disclosed in U.S. Pat. No. 4,185,042; and oxydipropylbis(trimethoxy silane) as disclosed in U.S. Pat. No. 4,379,891.

In one embodiment of the present invention, the coupling agent used can be an alkoxy silane of the general formula R_(x)—Si—(OR′)_(y), where x is 0 or 1, x+y=3 or 4, R and R′ are the same or different, R is selected from aryl, linear alkyl and branched alkyl hydrocarbon radicals, and R′ is selected from linear and branched alkyl hydrocarbon radicals. The aryl radicals preferably have from 6 to 12 carbon atoms. The alkyl radicals preferably have I to 12 carbon atoms, more preferably from 1 to 4 carbon atoms. Under melt conditions these alkoxy silane coupling agents can couple further to yield functionalities greater than 4. Preferred tetra alkoxy silanes are tetramethoxy silane (“TMSi”), tetraethoxy silane (“TESi”), tetrabutoxy silane (“TBSi”), and tetrakis(2-ethylhexyloxy)silane (“TEHSi”). Preferred trialkoxy silanes are methyl trimethoxy silane (“MTMS”), methyl triethoxy silane (“MTES”), isobutyl trimethoxy silane (“IBTMO”) and phenyl trimethoxy silane (“PhTMO”). Of these the more preferred are tetraethoxy silane and methyl trimethoxy silane.

In the embodiments of the present invention the polymer microstructure in the E and/or E₁ blocks is modified to control the vinyl content of the polymerized diene. This vinyl configuration can be achieved by the use of a control agent during polymerization of the diene. A typical agent is diethyl ether. See U.S. Pat. No. Re 27,145 and U.S. Pat. No. 5,777,031, the disclosure of which is hereby incorporated by reference. Any microstructure control agent known to those of ordinary skill in the art of preparing block copolymers to be useful can be used to prepare the block copolymers of the present invention.

In one embodiment the vinyl content is high. The block copolymers are prepared so that they have from about 60 to about 85 mol percent vinyl in the E and/or E₁ blocks prior to hydrogenation. In another embodiment, the block copolymers are prepared so that they have from about 65 to about 85 mol percent vinyl content. In still another embodiment, the block copolymers are prepared so that they have from about 70 to about 85 mol percent vinyl content. Another embodiment of the present invention includes block copolymers prepared so that they have from about 73 to about 83 mol percent vinyl content in the E and/or E, blocks.

In another embodiment the block copolymer of the present invention has a vinyl content from about 25 to about 59 mol percent in the E and/or E₁ blocks prior to hydrogenation. In this embodiment the preferred vinyl content is from about 35 to about 50 mol percent and in the most preferred embodiment the vinyl content is from 37 to 47 mol percent in the E and/or E₁ blocks.

In one embodiment, the present invention is a hydrogenated block copolymer. The hydrogenated block copolymers of the present invention are selectively hydrogenated using any of the several hydrogenation processes know in the art. For example the hydrogenation may be accomplished using methods such as those taught, for example, in U.S. Pat. Nos. 3,494,942; 3,634,594; 3,670,054; 3,700,633; and Re. 27,145, the disclosures of which are hereby incorporated by reference. Any hydrogenation method that is selective for the double bonds in the conjugated polydiene blocks, leaving the aromatic unsaturation in the polystyrene blocks substantially intact, can be used to prepare the hydrogenated block copolymers of the present invention.

The methods known in the prior art and useful for preparing the hydrogenated block copolymers of the present invention involve the use of a suitable catalyst, particularly a catalyst or catalyst precursor comprising an iron group metal atom, particularly nickel or cobalt, and a suitable reducing agent such as an aluminum alkyl. Also useful are titanium based catalyst systems. In general, the hydrogenation can be accomplished in a suitable solvent at a temperature within the range from about 20° C. to about 100° C., and at a hydrogen partial pressure within the range from about 100 psig (689 kPa) to about 5,000 psig (34,473 kPa). Catalyst concentrations within the range from about 10 ppm to about 500 ppm by wt of iron group metal based on total solution are generally used and contacting at hydrogenation conditions is generally continued for a period of time with the range from about 60 to about 240 minutes. After the hydrogenation is completed, the hydrogenation catalyst and catalyst residue will, generally, be separated from the polymer.

In the practice of the present invention, the hydrogenated block copolymers have a hydrogenation degree greater than 80 percent. This means that more than from 80 percent of the conjugated diene double bonds in the E or E₁ block has been hydrogenated from an alkene to an alkane. In one embodiment, the E or E₁ block has a hydrogenation degree greater than about 90 percent. In another embodiment, the E or E₁ block has a hydrogenation degree greater than about 95 percent.

In the practice of the present invention, the styrene content of the block copolymer is from about 13 percent to about 25 weight percent. In one embodiment, the styrene content of the block copolymer is from about 15 percent to about 24 percent. Any styrene content within these ranges can be used with the present invention. Subsequent to hydrogenation, from 0 to 10 percent of the styrene double bonds in the S blocks have been hydrogenated in the practice of the present invention.

The molecular weight of each of the S blocks in the block copolymers of the present invention is from about 5,000 to about 7,000 in the block copolymers of the present invention. In one embodiment, the molecular weight of each of the S blocks is from about 5,800 to about 6,600. The S blocks of the block copolymers of the present invention can be a polystyrene block having any molecular weight within these ranges.

In the practice of the present invention, the E blocks are a single polydiene block. These polydiene blocks can have molecular weights that range from about 40,000 to about 70,000. The E₁ block is a polydiene block having a molecular weight range of from about 20,000 to about 35,000. In one embodiment, the molecular weight range of the E block is from about 45,000 to about 60,000, and the molecular weight range for each E₁ block of a coupled block copolymer, prior to being coupled, is from about 22,500 to about 30,000.

One advantage of the present invention over conventional elastomeric compounds comprising hydrogenated block copolymer is that the inventive elastomeric compounds have high melt flows that allow them to be easily molded or continuously extruded into shapes or films or spun into fibers. This property allows end users to avoid or at least limit the use of additives that degrade properties, cause area contamination, smoking, and even build up on molds and dies.

For the purposes of the present invention, the term “melt index” is a measure of the melt flow of the polymer according ASTM D1238 at 230° C. and 2.16 kg weight. It is expressed in units of grams of polymer passing through a melt rheometer orifice in 10 minutes. The hydrogenated block copolymers of the present invention have a desirable high melt index allowing for easy processing. In one embodiment, the hydrogenated block copolymers of the present invention have a melt index of greater than or equal to 9. In another embodiment, the hydrogenated block copolymers of the present invention have a melt index of at least 15. In still another embodiment, the hydrogenated block copolymers of the present invention have a melt index of at least 40. Another embodiment of the present invention includes hydrogenated block copolymers having a melt index of from about 20 to about 100. Still another embodiment of the present invention includes hydrogenated block copolymers having a melt index of from about 50 to about 85.

The hydrogenated block copolymers of the present invention also are very low in contaminants that can cause these undesirable effects, such as diblocks from inefficient coupling. The block copolymers and hydrogenated block copolymers of the present invention have less than 15 weight percent of diblock content, such diblocks having the general formula: SE or SE₁ wherein S, E and E₁ are as previously defined. In one embodiment, the diblock level is less than 10 percent in another embodiment less than 8 percent. For example, where the structure of the hydrogenated block copolymer is (S-E₁)₂X, the block copolymer contains less than 10% of the S-E₁ species. All percentages are by weight.

One characteristic of the hydrogenated block copolymers of the present invention is that they have a low order-disorder temperature. The order-disorder temperature (ODT) of the hydrogenated block copolymers of the present invention is typically less than about 300° C. Above 300° C. the polymer is more difficult to process and can be subject to degradation during processing. ODT's of the block copolymer of 250° C. or less are preferred and ODT's of 225° C. or less are most preferred. For purposes of the present invention, the order-disorder temperature is defined as the temperature above which a zero shear viscosity can be measured by capillary rheology or dynamic rheology. Importantly, combinations of the hydrogenated block copolymers of the present invention with tackifiers, alpha-olefin copolymers, alpha-olefin terpolymers, waxes and the like can lead to blends having suitably low ODTs.

Exemplary thermoplastic polymers include polyolefin homo-, co- or terpolymers made by conventional Ziegler-Natta or single site metallocene catalysts. Example of such polyolefins are ethylene homopolymers, ethylene/alpha-olefin copolymers, propylene homopolymers, propylene/alpha-olefin copolymers, impact polypropylene copolymers, ethylene/propylene/alpha-olefin terpolymers, butylene homopolymers, butylene/alpha olefin copolymers, and other alpha olefin copolymers or interpolymers. In the present invention the alpha-olefin is 1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene and the like.

Representative polyethylenes include, for example, but are not limited to, substantially linear ethylene polymers, homogeneously branched linear ethylene polymers, heterogeneously branched linear ethylene polymers, including linear low density polyethylene (LLDPE), ultra or very low density polyethylene (ULDPE or VLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE) and high pressure low density polyethylene (LDPE).

When the thermoplastic polymer is polyethylene, the melt flow rate, also referred to as melt flow index, must be at least 25 g/10 min at 190° C. and 2.16 kg weight according to ASTM D1238. The preferred type of polyethylene is linear low density polyethylene.

Representative polypropylenes include, for example, but are not limited to, substantially isotactic propylene homopolymers, random alpha olefin/propylene copolymers where propylene is the major component on a molar basis and polypropylene impact copolymers where the polymer matrix is primarily a polypropylene homopolymer or random copolymer and the rubber phase is an alpha-olefin/propylene random copolymer. Suitable melt flow rates of polypropylenes are at least 10 g/10 min at 230° C. and 2.16 kg according to ASTM D1238. More preferred are melt flow rates of at least 20 g/10 min. Polypropylene homopolymers are the preferred type of polypropylene.

Terpolymers comprising styrene are also suitable and include ethylene/styrene/alpha olefins and propylene/styrene/alpha olefins. Suitable melt flow rates of styrene containing terpolymers are at least 10 g/10 min at 230° C. and 2.16 kg according to ASTM D1238.

Examples of ethylene/alpha-olefin copolymers, propylene/alpha-olefin copolymers and ethylene/propylene/alpha-olefin terpolymers include, but are not limited to, AFFINITY, ENGAGE and VERSIFY polymers from Dow Chemical and EXACT and VISTAMAXX polymers from Exxon Mobil. Suitable melt flow rates of such copolymers must be at least 10 g/10 min at 230° C. and 2.16 kg weight according to ASTM D1238. In the present invention inclusion of ethylene/alpha-olefin and propylene/alpha-olefin copolymers and ethylene/propylene/alpha-olefin terpolymers in the elastomeric compound serves to improve spinning performance, increase the tensile strength, and decrease the stickiness of the fibers. The amount of co- or terpolymer in the elastomer compound is from 5 to 90 wt %. When the elastomeric compound is made of a minority of co- or terpolymer the elastic properties, including tensile set and recovered energy, of the bicomponent fiber are optimal. The preferred amount of co- or terpolymer is from 5 to 49 wt % and the most preferred amount is from 5 to 20 wt %.

Still other thermoplastic polymers included herein are polyvinyl chloride (PVC) and blends of PVC with other materials, polyamides and polyesters such as poly(ethylene terephthalate), poly(butylene terephthalate) and poly(trimethylene terephthalate). Regardless of the specific type, the thermoplastic polymer must have a melt flow rate suitable for processing into fibers or components of fibers.

In the embodiments of the present invention it is especially useful to include resins compatible with the rubber E and/or E₁ blocks of the elastomeric compound. This serves to promote the flow of the elastomeric compound. Various resins are known, and are discussed, e.g., in U.S. Pat. Nos. 4,789,699; 4,294,936; and 3,783,072, the contents of which, with respect to the resins, are incorporated herein by reference. Any resin can be used which is compatible with the rubber E and/or E₁ blocks of the elastomeric compound and/or the polyolefin, and can withstand the high processing (e.g., extrusion) temperatures. Generally, hydrogenated hydrocarbon resins are preferred resins, because of their better temperature stability. Examples illustrative of useful resins are hydrogenated hydrocarbon resins such as low molecular weight, fully hydrogenated REGALREZ® (Eastman Chemical), ARKONO® (Arakawa Chemical) series resins, and terpene hydrocarbons such as ZONATAC®501 Lite (Arizona Chemical). The present invention is not limited to use of the resins listed here. In general, the resin may be selected from the group consisting of C₅ hydrocarbon resins, hydrogenated C₅ hydrocarbon resins, styrenated C₅ resins, C₅/C₉ resins, styrenated terpene resins, fully hydrogenated or partially hydrogenated C₉ hydrocarbon resins, rosins esters, rosins derivatives and mixtures thereof. One of ordinary skill in the art will understand that other resins which are compatible with the components of the composition and can withstand the high processing temperatures, and can achieve the objectives of the present invention, can also be used. The tackifier makes up the minor amount in the elastomer compound. The amount of tackifier is from 1 to 49 wt % basis the elastomer compound mass. When the amount of tackifier is less than 1 wt % the effect on elastomer compound flow is negligible. When the amount of tackifier is 50 wt % or greater the elastomeric properties of the bicomponent fiber are compromised. The preferred amount of tackifier is from 5 to 30 wt % and the most preferred is from 5 to 15 wt %.

The bicomponent fiber may also comprise a wax to promote flow and/or compatibility. Suitable waxes are those having a congealing point of from 50 to 70° C. Suitable amounts of wax are from 0.1 to 75% w, preferably from 5 to 60% wt based on the weight of the elastomeric compound. Animal, insect, vegetable, synthetic and mineral waxes may be used with those derived from mineral oils being preferred. Examples of mineral oil waxes include bright stock slack wax, medium machine oil slack wax, high melting point waxes and microcrystalline waxes. In the case of slack waxes up to 25% w of oil may be present. Additives to increase the congealing point of the wax may also be present.

When the elastomeric compound is composed of a hydrogenated block copolymer and other components such as tackifier resins, alpha-olefin copolymers, alpha-olefin terpolymers or other processing aids and additives, the elastomeric compound has a desirable high melt index allowing for easy processing In one embodiment, the elastomeric compounds of the present invention have a melt index of greater than or equal to 12. In another embodiment, the elastomeric compounds of the present invention have a melt index of at least 15. In still another embodiment, the elastomeric compounds of the present invention have a melt index of at least 40. Another embodiment of the present invention includes elastomeric compounds having a melt index of from about 20 to about 100. Still another embodiment of the present invention includes elastomeric compounds having a melt index of from about 50 to about 85.

The bicomponent fiber may also comprise a polymer extending oil. The oil may be incorporated to improve the processability of the fiber or to enhance its softness. Especially preferred are the types of oil that are compatible with the E and/or E₁ of the block copolymer. While oils of higher aromatics content are satisfactory, those petroleum-based white oils having low volatility and less than 50% aromatic content are preferred. The oils should additionally have low volatility, preferable having an initial boiling point above about 260° C. The amount of oil employed varies from about 0 to about 300 parts by weight per hundred parts by weight rubber, or block copolymer, preferably about 20 to about 150 parts by weight.

The elastomeric compound is typically stabilized by the addition of an antioxidant or mixture of antioxidants. Frequently, a sterically hindered phenolic stabilizer is used, or a phosphorus-based stabilizer is used in combination with a sterically hindered phenolic stabilizer, such as disclosed in Japanese patent No. 94055772; or a combination of phenolic stabilizers is used, such as disclosed in Japanese patent No. 94078376.

It is sometimes desirable to use processing aids and other additives in the elastomeric compound. Exemplary of such aids and additives are members selected from the group consisting of other block copolymers, olefin polymers, styrene polymers, fillers, reinforcements, lubricants, pigments, dyes, optical brighteners, bluing agents and flame retardants and mixtures thereof.

The bicomponent fibers of the present invention can be used to form a variety of articles. These articles include elastic mono filaments, woven fabrics, spun bond non-woven fabrics or filters, melt-blown fabrics, staple fibers, yarns, bonded, carded webs, and the like. Any of the processes typically used to make these articles can be employed when they are equipped to extrude two materials into a bicomponent fiber.

In particular, non-woven fabrics or webs can be formed by any of the processes known in the art. One process, typically referred to as spunbond, is well known in the art. U.S. Pat. No. 4,405,297 describes a typical spunbond processes. The spunbond process commonly comprises extruding the fibers from the melt through a spinneret, quenching and/or drawing the fibers using an air flow, and collecting and bonding the non-woven web. The bonding of the non-woven web is typically accomplished by any thermal, chemical or mechanical methods, including water entanglement and needle punch processes, effective in creating a multiplicity of intermediate bonds among the fibers of the web. The non-woven webs of the present invention can also be formed using melt-blown process such as described in U.S. Pat. No. 5,290,626. Carded webs may be formed from non-woven webs by folding and bonding the non-woven web upon itself in the cross machine direction.

The non-woven fabrics of the present invention can be used for a variety of elastic fabrics such as diapers, waistbands, stretch panels, disposable garments, medical and personal hygiene articles, filters, and the like.

Elastic mono-filaments of the present invention are continuous, single, bicomponent fibers used for a variety of purposes and can be formed by any of the known methods of the art comprising spinning, drawing, quenching and winding. As used herein, staple fiber means cut or chopped segments of the continuously coextruded bicomponent fiber.

Yarns of the bicomponent fibers can be formed by common processes. U.S. Pat. No. 6,113,825 teaches the general process of yarn formation. In general, the process comprises melt extrusion of multiple fibers from a spinneret, drawing and winding the filaments together to form a multi-filament yarn, extending or stretching the yarn optionally through one or more thermal treatment zones, and cooling and winding the yarn.

The articles of the present invention can be used alone or in combination with other articles made with the bicomponent fibers or with other classes of materials. As an example, non-woven webs can be combined with elastic mono-filaments to provide elastic stretch panels. As another example, non-woven webs can be bonded to other non-elastomeric non-woven webs or polymeric films of many types.

In the process of producing the bicomponent fiber of the present invention two separate single screw extruders are used to extrude the sheath polymer and core polymer into two separate melt pumps. Following the melt pumps, the polymers are brought together into their bicomponent configuration in the spinneret via a series of plates and baffles. Upon exiting the spinneret the fibers are cooled/quenched via a cold air quench cabinet. After quenching the fibers are drawn via an aspirator or a series of cold rolls. In the case that cold rolls are used, the fibers are taken up onto a winder. In the case that an aspirator is used, the fibers are allowed to collect in a drum beneath the aspirator.

One important aspect of the process is the rate at which the bicomponent fibers may be produced. The high flow characteristics presented by the inventive fibers allows high extrusion rates. This is important from a practical sense since commercial equipment operates at high extrusion rates. In this way, economic throughputs can be achieved. With the bicomponent fiber compositions of the present invention spinning speeds of greater than 800 meters per minute (mpm) are achieved. The more preferred spees are about 1000 mpm or greater and the most preferred speeds are about 1500 mpm or greater.

For the applications disclosed herein, fine diameter fibers are preferred. These fine diameter fibers are extremely efficient elastic materials in the sense that very small amounts of material can be used to affect elastic behavior in articles so composed. The fine diameter fibers may be a single bicomponent fiber or may be composed of multiple bicomponent filaments. In the present invention bicomponent fibers having a denier (grams per 9000 m fiber or filament) from 0.1 to 30 can be made. More preferred are fibers having a denier from 0.5 to 20 and most preferred are fibers having a denier from 1 to 10.

EXAMPLES

The term “elastic” is used herein to mean any material which, upon application of a biasing force, is stretchable, that is, elongatable at least about 60 percent (i.e., to a stretched, biased length which is at least about 160 percent of its relaxed unbiased length) and which, will recover at least 40 percent of its elongation upon release of the stretching, elongating force. A hypothetical example would be a one (1) inch sample of a material which is elongatable to at least 1.60 inches (4.06 cm) and which, upon being elongated to 1.60 inches (4.06 cm) and released, will recover to a length of not more than 1.27 inches (3.23 cm). Many elastic materials may be elongated by much more than 60 percent (i.e., much more than 160 percent of their relaxed length), for example, elongated 100 percent or more, and many of these will recover to substantially their initial relaxed length, for example, to within 105 percent of their initial relaxed length, upon release of the stretching force.

The elasticity was measured on yarns formed from the bicomponent fibers as the percent strain recovery at 100 percent elongation. The yarn consisted of a multiplicity of individual continuous bicomponent filaments ranging in number from 36 to 144 depending upon the number of holes in the spinneret. The yarn was stretched manually to 100% elongation and then allowed to relax. The relaxed length of the yarn was then measured and the percent recovery calculated. In this method the elasticity is determined as the percent recovery.

As used herein, the term “tenacity” refers to the measure of tensile strength of a yarn as measured in grams per denier.

Examples 1-8

Bicomponent fibers with a polypropylene sheath and a SEBS elastomer core at sheath/core ratios of 30/70 and 20/80 were made according to the following description. The polypropylene sheath was a nominal 38 MFR homopolymer (5D49) from The Dow Chemical Company. The elastomer core (Polymer 7) was a nominal 50 MFR, high vinyl (vinyl content=75 mol %), coupled SEBS copolymer (coupling efficiency=96%) with an 18% styrene content, a styrene MW of 6600 and a midblock molecular weight of 60,000.

The fibers were made using a conventional, commercial-type high speed spinning process using bicomponent technology and spinnerets from Hills Inc.

Table 1 gives typical spinning performance and mechanical properties of the fibers. From Table 1, one can see that high speed spinning can be achieved (Examples 3 5, and 8) as well as reasonable fiber tensile strength and elongation-to-break (Examples 1, 2, 4, 6, 7). Exceptionally high spinning speeds were attainable. The sheath-core bicomponent fibers (Examples 3 and 5) were spun at 2700 mpm.

Examples 9-13

Bicomponent fibers with a polypropylene sheath and a SEBS elastomer core at sheath/core ratios of 30/70 and 20/80 were made according to the following description. The polypropylene sheath was a nominal 38 MFR homopolymer (5D49) from The Dow Chemical Company. The elastomer core (Polymer 5) was a 31 MFR, high vinyl (vinyl content=76%), coupled SEBS copolymer (coupling efficiency=94%) with an 18% styrene content, a styrene MW of 6200 and a midblock molecular weight of 56,000.

The fibers were made via a conventional, commercial-type high speed spinning process using bicomponent technology and spinnerets from Hills Inc.

Good tensile properties could be achieved with the 31 MFR elastomer (Examples 9, 11 and 12). The attainable spinning speed was in the range of 1500 to 1800 mpm.

Examples 14-25

Bicomponent fibers with a polypropylene sheath and a SEBS elastomer core at sheath/core ratios of 30/70 and 20/80 were made according to the following description. The polypropylene sheath was a nominal 38 MFR homopolymer (5D49) from The Dow Chemical Company. The elastomer core (Polymer 6) was a nominal 20 MFR, high vinyl (vinyl content=76%), coupled SEBS copolymer (coupling efficiency=95%) with an 19% styrene content, a styrene MW of 6100 and a midblock molecular weight of 50,000.

The fibers were made via a conventional, commercial-type high speed spinning process using bicomponent technology and spinnerets from Hills Inc.

The results of Table 3 demonstrate that a lower melt flow elastomer has a detrimental effect on the spinning performance (maximum spinning speed) but the tensile properties are still considered to be reasonable for an elastic fiber. Table 3 also shows that as the polypropylene becomes a greater portion of the fiber cross-section that spinning performance improves and that even relatively low melt flow elastomers can offer good spinning performance with the correct sheath/core ratio. In addition, the polypropylene improves the tensile strength of the fibers as its concentration increases but probably has a negative effect on the fiber elasticity.

Examples 26-36

Bicomponent fibers with a polypropylene sheath and a SEBS elastomer core at sheath/core ratios of 30/70 and 20/80 were made according to the following description. The polypropylene sheath was a nominal 38 MFR homopolymer (5D49) from The Dow Chemical Company. The elastomer core was a blend with polypropylene (5D49) and an elastomer (Polymer 7). Blend 1 was a blend of 10 wt % Dow 5D49 polyproplene with 90 wt % Polymer 7. Blend 2 was a blend of 20 wt % Dow 5D49 polypropylene with 80 wt % Polymer 7.

The fibers were made via a conventional, commercial-type high speed spinning process using bicomponent technology and spinnerets from Hills Inc. Table 4 demonstrates that elastomer blends with polypropylene made good elastomeric cores for bicomponent elastic fibers. High spinning speeds and good tensile and elastic properties were achieved.

A comparative monocomponent fiber (Example 36) is also shown in Table 4. The monocomponent fiber consisted only of the elastomer compound (Polymer 7) and no thermoplastic polymer sheath. Low spinning speeds were required and the fibers exhibited unacceptable stickiness during the spinning process. The resulting monocomponent fibers self-adhered and could not be separated.

Examples 37-39

Bicomponent fibers were also spun via a single air aspirator to simulate a spunbond process. Air pressure in the aspirator was used to affect the maximum spinning speed, i.e., the higher the pressure the higher the spinning speed. For all of the examples the polymer throughput per hole (0.35 g/hole/min) is the same.

Example 37 was a comparative monocomponent fiber of 5D49 polypropylene alone. The maximum air pressure reached 40 psi before fibers began to break. The fibers of this thermoplastic polymer had little or no elasticity.

Example 38 used a 5D49 polypropylene sheath and a 50 MFR elastic core (Polymer 7) at a 20/80 ratio to produce elastic spunbond fibers. The maximum spinning speed was 20 psi before filaments began to break. Example 39 was a bicomponent fiber of polypropylene (5D49) and a 20 MFR elastomer (Polymer 6) at a sheath/core ratio of 40/60. The maximum spinning speed was 25 psi before fibers began to break. The bicomponent fibers of Examples 38 and 39 were elastic.

Example 40-45

Examples 40 through 44 demonstrate sheath/core bicomponent fibers using Dow ASPUN polyethylene as the thermoplastic polymer sheath (6811A) and Polymer 7 as the elastomeric core. These examples demonstrate that polyethylene can also be used as a sheath for bicomponent elastic fibers.

The fibers were made via a conventional, commercial-type high speed spinning process using bicomponent technology and spinnerets from Hills Inc.

Example 46

A bicomponent elastic fiber was made with a relatively low melt flow rate, low vinyl elastomer (Polymer 8) according to the following description. Polymer 8 was a nominal 9 MFR, 38% vinyl coupled SEBS elastomer. It has a styrene block molecular weight of 5000, a midblock molecular weight of 47,000, and a coupling efficiency of 94%. The nominal styrene content is 18 wt %. The sheath for this fiber is a nominal 12 MFR homopolymer polypropylene.

Examples 47-55

Bicomponent filaments were made having a polypropylene sheath and a SEBS elastomer core at sheath/core ratios of 30/70 and 20/80. The polypropylene sheath was a nominal 38 MFR homopolymer (5D49) from The Dow Chemical Company. The elastomer core is a blend of 90 wt % high vinyl SEBS block copolymer (Polymer 1) and 10 wt % Regalrez 1126 tackifier. Polymer 1 had a nominal 20% styrene content, a styrene MW of 6,200 daltons and a midblock molecular weight of 50,000 daltons. The vinyl content of the EB block was 77%. The blended elastomeric compound had a melt flow of 55 g/10 min. The filaments were made via a conventional high speed spinning process using bicomponent technology and spinnerets from Hills Inc. Table 8 gives typical spinning performance and mechanical properties of the filaments. The spinneret hole size was 0.35 mm with 72 holes. Table 8 shows that high speed spinning can be achieved (Examples 49, 50, 51, 53, 54 and 55) as well as reasonable fiber tensile strength and elongation to break. The fibers in these examples exhibited fair to good elasticity.

Examples 56-62

Examples 56-62 were bicomponent sheath/core fibers made with a polypropylene sheath and a SEBS copolymer/tackifier blend as the core according to the method of Examples 47-55. The SEBS copolymer (Polymer 2) was a nominal 40% vinyl (1,2 butadiene addition), 22% styrene block copolymer. The styrene peak molecular weight was approximately 5300 daltons and the midblock peak molecular weight was approximately 38,000 daltons. The tackifier was Regalrez 1126. The melt flow of the Polymer 2/tackifier blended elastomeric compound was 50 g/10 min with 10 wt % tackifier and 90 wt % Polymer 2. Compared to Examples 47-55, Examples 56-62 were measurably stronger (tenacity) but had similar elongation to break (toughness) and elasticity. At a 10/90 sheath/core ratio the tensile strength decreased but the elasticity increased significantly because the rubber content was higher.

Example 63

Example 63 was a bicomponent sheath/core fiber with a polypropylene sheath and a VISTAMAXX® polypropylene (VM2125)/Polymer 1 blend as the core according to the method. The blend was 25 wt % VISTAMAXX propropylene and 75 wt % Polymer 1. The melt flow of Polymer 1 was_(—)24 g/10 min. The melt flow of the blended elastomeric compound was_(—)32 g/10 min. Example 63 in Table 10 demonstrates that the VISTAMAXX/block copolymer blend is melt spinnable and that reasonable fiber properties are attainable. TABLE 1 Spinning Elongation Highest Denier per Sheath/Core Speed Tenacity at Break Elasticity Spinning Spinneret filament Example Ratio (mpm) (g/dn) (%) (%) Speed # of holes (dpf) 1 20/80  500 0.3 500 70 — 72 15 2 20/80 1400 0.6 320 80 — 72   5.4 3 20/80 — — — — 2700 72 — 4 30/70  500 0.3 550 — — 72 15 5 30/70 — — — — 2700 72 — 6 20/80  500 0.2 560 — — 36 27 7 20/80 1500 0.3 280 — — 36   7.6 8 20/80 — — — — 3000 36 —

TABLE 2 Spinning Elongation Highest Sheath/Core Speed Tenacity at Break Elasticity Spinning Example Ratio (mpm) (g/dn) (%) (%) Speed 9 20/80 500 0.3 470 — — 10 20/80 — — — — 1500 11 30/70 500 0.3 570 — — 12 30/70 1400  0.7 250 75 — 13 30/70 — — — — 1800

TABLE 3 Spinning Elongation Highest Denier per Sheath/Core Speed Tenacity at Break Elasticity Spinning filament Example Ratio (mpm) (g/dn) (%) (%) Speed (dpf) 14 20/80  500 0.3 500 — — 14.5 15 20/80 1000 0.5 310 — —  7.5 16 20/80 — — — — 1100 — 17 30/70  500 0.3 490 — — 14.5 18 30/70 1400 0.7 250 80 — 5  19 30/70 — — — — 1500 — 20 40/60  500 0.5 660 — — 14.5 21 40/60 1400 0.8 320 — — 5  22 40/60 — — — — 1900 — 23 50/50  500 0.5 660 — — 14.5 24 50/50 1400 0.9 330 50 — 5  25 50/50 — — — — 2500 —

TABLE 4 Highest Spinning Elongation Spinning Sheath/Core Speed Tenacity at Break Elasticity Speed Comments/denier per Example Core Ratio (mpm) (g/dn) (%) (%) (mpm) filament (dpf) 26 Blend 1 0/100 — — — — 800 No sheath, very sticky 27 Blend 1 20/80  500 0.1 660 — —  21 dpf 28 Blend 1 20/80 1500 0.2 310 75 — 7.7 dpf 29 Blend 1 20/80 2000 0.4 200 — —   6 dpf 30 Blend 1 20/80 — — — — 2700  — 31 Blend 2 0/100 — — — — 800 No sheath, very sticky 32 Blend 2 20/80  500 0.2 530 — —  21 dpf 33 Blend 2 20/80 1500 0.3 200 70 — 7.7 dpf 34 Blend 2 20/80 2000 0.4 160 75 —   6 dpf 35 Blend 2 20/80 — — — — 3000  — 36 Polymer 7 0/100 — — — — 800 No sheath, very sticky

TABLE 5 Sheath/ Max Spinning Core Speed Elasticity Example Sheath Core Ratio (psi) (%) 37 5D49 — 100/0  40 20 38 5D49 Polymer 7 20/80 20 — 39 5D49 Polymer 6 40/60 25 75

TABLE 6 Denier Spinning per Elongation Highest Sheath/Core Speed filament Tenacity at Break Elasticity Spinning Example Ratio (mpm) (g/9000 m) (g/dn) (%) (%) Speed 40 20/80 300 17.6 0.1 660 — — 41 20/80 500 11.6 0.1 680 — — 42 20/80 — — — — —  500 43 30/70 500 11.6 0.1 580 60 — 44 30/70 1000   5.2 0.2 360 50 — 45 30/70 — — — — — 1000

TABLE 7 Spinning Elongation Sheath/Core Speed Tenacity at Break Elasticity Example Ratio (mpm) (g/dn) (%) (%) 46 20/80 500 0.02 480 80

TABLE 8 Spinning Elongation Denier Per Sheath/Core Speed Tenacity at Break Filament Example Ratio (mpm) (g/dn) (%) Elasticity (dpf) 47 30/70 1500 0.7 320 50 5.2 48 30/70 2000 0.8 250 50 3.8 49 30/70 2500 0.9 250 50 3.3 50 30/70 3000 0.9 120 50 2.7 51 30/70 3500 1.2 180 50 2.3 52 20/80 1500 0.6 260 60 5.2 53 20/80 2500 0.8 170 60 3.3 54 20/80 3000 1.0 160 40 2.5 55 20/80 3500 0.9 140 40 2.4

TABLE 9 Sheath/ Spinning Elongation Core Speed Tenacity at Break Example ratio (mpm) (g/dn) (%) elasticity dpf 56 30/70 1500 1.1 300 40 5.2 57 30/70 2500 2.2 200 40 3.1 58 30/70 3000 2.1 170 40 2 59 20/80 1500 1.1 330 70 5.3 60 20/80 2500 1.7 230 60 3 61 20/80 3000 1.6 180 60 2.6 62 10/90 1500 0.9 390 90 4.3

TABLE 10 Sheath/ Spinning Elongation Core Speed Tenacity at Break Example Ratio (mpm) (g/dn) (%) dpf Elasticity 63 20/80 1500 0.6 230 5.1 70 

1. A bicomponent fiber comprising a thermoplastic polymer and an elastomeric compound wherein the elastomeric compound consists essentially of a selectively hydrogenated block copolymer having an S block and an E or E₁ block and having the general formula: S-E-S, (S-E₁)_(n), (S-E₁)_(n)S, (S-E₁)_(n)X or mixtures thereof, wherein: a. prior to hydrogenation the S block is a polystyrene block; b. prior to hydrogenation the E block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof, having a molecular weight from 40,000 to 70,000; c. prior to hydrogenation the E₁ block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene, and mixtures thereof, having a molecular weight from 20,000 to 35,000; d. n has a value of 2 to 6 and X is the residue of a coupling agent; e. the styrene content of the block copolymer is from 13 to 25 weight percent; f. the vinyl content of the polydiene block prior to hydrogenation is from 70 to 85 mol percent; g. the block copolymer includes less than 15 weight percent of units having the general formula: S-E or S-E₁ wherein S, E and E₁ are as already defined; h. subsequent to hydrogenation about 0 to 10% of the styrene double bonds have been hydrogenated and at least 80% of the conjugated diene double bonds have been hydrogenated; i. the molecular weight of each of the S blocks is from 5,000 to 7,000 and a tackifying resin.
 2. The bicomponent fiber of claim 1 wherein the melt index of the block copolymer is greater than or equal to 9 grams/10 minutes according to ASTM D1238 at 230° C. and 2.16 kg weight.
 3. The bicomponent fiber of claim 1 wherein the tackifying resin is from 5 to 30 wt % basis the elastomeric compound mass.
 4. The bicomponent fiber of claim 1 wherein the polystyrene content of the block copolymer is from 15 to 24 weight percent.
 5. The bicomponent fiber of claim 1 wherein the polydiene blocks E and E₁ have a vinyl content from 73 to 83 mol percent.
 6. The bicomponent fiber of claim 1 wherein the molecular weight of the polystyrene block S is from 5,800 to 6,600.
 7. The bicomponent fiber of claim 1 wherein the E block is polybutadiene having a molecular weight from 45,000 to 60,000, or the E₁ block is two or more coupled polybutadiene blocks, each of the polybutadiene blocks, prior to being coupled, has a molecular weight from 22,500 to 30,000.
 8. The bicomponent fiber of claim 1 wherein the structure of the selectively hydrogenated block copolymer is (S-E₁)_(n)X and the block copolymer contains less than 10% of an uncoupled S-E₁ species.
 9. The bicomponent fiber of claim 7 wherein the coupling agent is selected from the group consisting of tetramethoxy silane, tetraethoxy silane, tetrabutoxy silane, tetrakis(2-ethylhexyloxy) silane, methyl trimethoxy silane, methyl triethoxy silane, isobutyl trimethoxy silane, phenyl trimethoxy silane, silicon tetrachloride, methyl-trichlorosilane and dimethyl-dichlorosilane.
 10. The bicomponent fiber of claim 1 wherein the melt flow rate of the block copolymer is at least 15 g/10 min at 230° C. and 2.16 kg weight according to ASTM D1238.
 11. The bicomponent fiber of claim 1 wherein the melt flow rate of the block copolymer is at least 40 g/10 min at 230° C. and 2.16 kg weight according to ASTM D1238.
 12. The bicomponent fiber of claim 1 wherein the thermoplastic polymer is selected from the group consisting of polypropylene, polyethylene, polyamides, poly(ethylene terephthalate), poly(butylene terephthalate), and poly(trimethylene terephthalate).
 13. The bicomponent fiber of claim 12 wherein the thermoplastic-polymer is polypropylene having a melt flow of at least 20 g/10 min at 230° C. and 2.16 kg according to ASTM D1238.
 14. The bicomponent fiber of claim 12 wherein the thermoplastic polymer is linear low density polyethylene having a melt flow of at least 25 g/10 min at 190° C. and 2.16 kg according to ASTM D1238.
 15. The bicomponent fiber of claim 1 having a sheath-core morphology wherein the core consists of the elastomeric compound and the sheath consists primarily of the thermoplastic polymer.
 16. The bicomponent fiber of claim 15 wherein the volume ratio of thermoplastic polymer sheath to elastomeric compound core is from 1/99 to 50/50.
 17. The bicomponent fiber of claim 1 having an islands-in-the-sea morphology wherein the islands consist primarily of the elastomeric compound and the sea consists primarily of the thermoplastic polymer.
 18. The bicomponent fiber of claim 17 wherein the volume ratio of thermoplastic polymer sea to elastomeric compound islands is from 1/99 to 50/50.
 19. The bicomponent fiber of claim 1 having a denier from 0.5 to
 20. 20. An article comprising the bicomponent fiber of claim 1 which is an elastic mono-filament, a woven fabric, a spun bond non-woven fabric, a melt-blown non-woven fabric or filter, a staple fiber, a yarn or a bonded, carded web.
 21. A bicomponent fiber comprising a thermoplastic polymer and an elastomeric compound wherein the elastomeric compound consists essentially of a selectively hydrogenated block copolymer having an S block and an E or E₁ block and having the general formula: S-E-S, (S-E₁)_(n), (S-E₁)_(n)S, (S-E₁)_(n)X or mixtures thereof, wherein: a. prior to hydrogenation the S block is a polystyrene block; b. prior to hydrogenation the E block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof, having a molecular weight from 40,000 to 70,000; c. prior to hydrogenation the E₁ block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene, and mixtures thereof, having a molecular weight from 20,000 to 35,000; d. n has a value of 2 to 6 and X is the residue of a coupling agent; e. the styrene content of the block copolymer is from 13 to 25 weight percent; f. the vinyl content of the polydiene block prior to hydrogenation is from 35 to 50 mol percent; g. the block copolymer includes less than 15 weight percent of units having the general formula: S-E or S-E₁ wherein S, E and E₁ are as already defined; h. subsequent to hydrogenation about 0 to 10% of the styrene double bonds have been hydrogenated and at least 80% of the conjugated diene double bonds have been hydrogenated; i. the molecular weight of each of the S blocks is from 5,000 to 7,000 and any one of a tackifying resin, an alpha-olefin copolymer, an alpha-olefin terpolymer, a wax or mixtures thereof.
 22. The bicomponent fiber of claim 21 wherein the melt index of the elastomeric compound is greater than or equal to 15 grams/10 minutes according to ASTM D1238 at 230° C. and 2.16 kg weight.
 23. The bicomponent fiber of claim 21 wherein the melt index of the elastomeric compound is at least 40 grams/10 minutes according to ASTM D1238 at 230° C. and 2.16 kg weight.
 24. The bicomponent fiber of claim 21 wherein the alpha-olefin copolymer is selected from the group consisting of ethylene/alpha-olefin copolymers and propylene/alpha-olefin copolymers.
 25. The bicomponent fiber of claim 21 wherein the alpha-olefin terpolymer is selected from the group consisting of ethylene/propylene/alpha-olefin terpolymers, ethylene/styrene/alpha-olefin terpolymers and propylene/styrene/alpha-olefin terpolymers.
 26. The bicomponent fiber of claim 21 wherein the tackifying resin, alpha-olefin copolymer or alpha-olefin terpolymer is from 5 to 30 wt % basis the elastomeric compound mass.
 27. The bicomponent fiber of claim 21 having a sheath-core morphology wherein the core consists of the elastomeric compound and the sheath consists primarily of the thermoplastic polymer.
 28. The bicomponent fiber of claim 27 wherein the volume ratio of thermoplastic polymer sheath to elastomeric compound core is from 1/99 to 50/50.
 29. The bicomponent fiber of claim 21 having an islands-in-the-sea morphology wherein the islands consist primarily of the elastomeric compound and the sea consists primarily of the thermoplastic polymer.
 30. The bicomponent fiber of claim 29 wherein the volume ratio of thermoplastic polymer sea to elastomeric compound islands is from 1/99 to 50/50.
 31. The bicomponent fiber of claim 21 having a denier from 0.5 to
 20. 32. An article comprising the bicomponent fiber of claim 21 which is an elastic mono-filament, a woven fabric, a spun bond non-woven fabric, a melt-blown non-woven fabric or filter, a staple fiber, a yarn or a bonded, carded web.
 33. A bicomponent fiber comprising a thermoplastic polymer and an elastomeric compound wherein the elastomeric compound consists essentially of a selectively hydrogenated block copolymer having an S block and an E or E₁ block and having the general formula: S-E-S, (S-E₁)., (S-E₁)_(n)S, (S-E₁)_(n)X or mixtures thereof, wherein: a. prior to hydrogenation the S block is a polystyrene block; b. prior to hydrogenation the E block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof, having a molecular weight from 40,000 to 70,000; c. prior to hydrogenation the E₁ block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene, and mixtures thereof, having a molecular weight from 20,000 to 35,000; d. n has a value of 2 to 6 and X is the residue of a coupling agent; e. the styrene content of the block copolymer is from 13 to 25 weight percent; f. the vinyl content of the polydiene block prior to hydrogenation is from 70 to 85 mol percent; g. the block copolymer includes less than 15 weight percent of units having the general formula: S-E or S-E₁ wherein S, E and E₁ are as already defined; h. subsequent to hydrogenation about 0 to 10% of the styrene double bonds have been hydrogenated and at least 80% of the conjugated diene double bonds have been hydrogenated; i. the molecular weight of each of the S blocks is from 5,000 to 7,000 and any one of an alpha-olefin copolymer, an alpha-olefin terpolymer, a wax or mixtures thereof.
 34. The bicomponent fiber of claim 33 wherein the melt index of the block copolymer is greater than or equal to 9 grams/10 minutes according to ASTM D1238 at 230° C. and 2.16 kg weight.
 35. The bicomponent fiber of claim 33 wherein the alpha-olefin copolymer is selected from the group consisting of ethylene/alpha-olefin copolymers and propylene/alpha-olefin copolymers.
 36. The bicomponent fiber of claim 33 wherein the alpha-olefin terpolymer is selected from the group consisting of ethylene/propylene/alpha-olefin terpolymers, ethylene/styrene/alpha-olefin terpolymers and propylene/styrene/alpha-olefin terpolymers.
 37. The bicomponent fiber of claim 33 wherein the alpha-olefin copolymer or alpha-olefin terpolymer is from 5 to 49 wt % basis the elastomeric compound mass.
 38. The bicomponent fiber of claim 33 having a sheath-core morphology wherein the core consists of the elastomeric compound and the sheath consists primarily of the thermoplastic polymer.
 39. The bicomponent fiber of claim 33 wherein the volume ratio of thermoplastic polymer sheath to elastomeric compound core is from 1/99 to 50/50.
 40. The bicomponent fiber of claim 33 having an islands-in-the-sea morphology wherein the islands consist primarily of the elastomeric compound and the sea consists primarily of the thermoplastic polymer.
 41. The bicomponent fiber of claim 40 wherein the volume ratio of thermoplastic polymer sea to elastomeric compound islands is from 1/99 to 50/50.
 42. The bicomponent fiber of claim 33 having a denier from 0.5 to
 20. 43. An article comprising the bicomponent fiber of claim 33 which is an elastic mono-filament, a woven fabric, a spun bond non-woven fabric, a melt-blown non-woven fabric or filter, a staple fiber, a yarn or a bonded, carded web. 